Page 71. Is StandardScaler the default scaling for ColumnTransformer?

I noticed on page 71 that when the `ColumnTransformer` is used the `StandardScaler` method was not specified.

```python
from sklearn.compose import ColumnTransformer

num_attribs = list(housing_num)
cat_attribs = ["ocean_proximity"]

full_pipeline = ColumnTransformer([
("num", num_pipeline, num_attribs),
("cat", OneHotEncoder(), cat_attribs),
])

housing_prepared = full_pipeline.fit_transform(housing)
```

Whereas, on the previous page, without using `ColumnTransformer`:

```python
from sklearn.pipeline import Pipeline
from sklearn.preprocessing import StandardScaler

num_pipeline = Pipeline([
('imputer', SimpleImputer(strategy="median")),
('attribs_adder', CombinedAttributesAdder()),
('std_scaler', StandardScaler()), # <==
])

housing_num_tr = num_pipeline.fit_transform(housing_num)
```

Checking the Sklearn documentation I was not able to clarify this.

Thank You
Tom